Wall Street wobbles as health stocks, oil prices drop | Reuters

Wall Street struggled for gains in volatile trading on Monday, weighed down by healthcare stocks and oil prices hitting fresh 12-year lows, ahead of the start of corporate earnings season.

The S&P energy sector down 2.23 percent, and materials sector, off 1.6 percent, faced the brunt of a near 6 percent slide in oil prices.

The health sector was down 1.38 percent, dragged down by Celgene and McKesson. The utilities sector's 0.65 percent gain led the four advancing S&P sectors.

U.S. stocks opened higher, coming off their worst-ever start to a year on mounting investor concerns about declining oil prices and a China-led slowdown in global growth.

Even strong December U.S. nonfarm payrolls data on Friday failed to boost investor optimism.

"None of us know what the future is, but given this moment, where we've gotten very conflicting data, it makes investors nervous," said Kim Forrest, senior equity research analyst at Fort Pitt Capital Group in Pittsburgh.

"I think the final coup de grâce is the Federal Reserve and its tightening phase has made them even more nervous."

At 12:43 p.m. ET (1743 GMT), the Dow Jones industrial average was down 16.43 points, or 0.1 percent, at 16,330.02.

The S&P 500 was down 6.85 points, or 0.36 percent, at 1,915.18 and the Nasdaq Composite index was down 29.17 points, or 0.63 percent, at 4,614.46.

Celgene fell 5.8 percent to $102.66 and McKesson dropped 9.9 percent to $164.38 after both companies gave disappointing profit forecasts.

Exxon and Chevron were both off nearly 2 percent on weak oil prices. Exxon was the biggest drag on the S&P.

Among materials stocks, Freeport-McMoRan tumbled 17 percent, while Caterpillar and DuPont were down nearly 3 percent, weighing the most on the Dow.

Alcoa, down 0.5 percent at $8.04, is scheduled to report fourth-quarter results after the close, unofficially starting the earnings season.

The aluminum producer's performance is regarded as a barometer of results from other materials and industrial companies.

Energy and materials companies are expected to be main drivers behind U.S. corporate earnings moving into a recession - two quarters of falling profits - in the fourth quarter.